1. Field of Invention
The invention relates to a linear motion module.
2. Related Art
In the linear motion module, a ball circulation passage is disposed so that the sliding block can move frontward on the linear rail through the balls of a limited number. By the ball circulation passage, the balls can return to between the linear rail and the sliding block so as to function again after the sliding block moves.
FIG. 1 is a sectional diagram of a conventional linear motion module. As shown in FIG. 1, the linear motion module 1 includes a linear rail 11, a sliding block 12 and a plurality of balls 13. The linear rail 11 is configured with a rail groove 111, the inside of the sliding block 12 is configured with an inner circulation groove 121, and the rail groove 111 and the inner circulation groove 121 constitute an inner circulation passage R for the balls moving through. Besides, the sliding block 12 is configured with an outer circulation passage 122. The balls 13 sequentially pass through a circulation guiding curve (not shown) and the outer circulation passage 122 and then return to between the linear rail 11 and the sliding block 12.
In the prior art, the drilling machining is used to form the outer circulation passage 122 for the highly-rigid sliding block 12. During the process, an end surface of the sliding block 12 is regarded as the base surface and the drilling is performed on the other end surface to form the outer circulation passage 122 penetrating through the sliding block 12 to, or the two end surfaces are alternately regarded as the base surfaces and the drillings are performed on the two end surfaces so that the holes can communicate with each other to form the outer circulation passage 122.
However, there are some problems for the conventional art to form the outer circulation passage. First, the drilling machining easily causes the taper at the two ends of the outer circulation passage, so the passage diameter is not uniform and the circulation motion of the balls is thus unstable. Second, because the drilling machining can not be completed just by a single end surface, the sectional difference will occur in the passage and therefore the smooth level of the outer circulation passage is decreased. The above-mentioned problems also result in the much noise, pause and/or instability during the motion of the linear motion module and even result in the damage of the components.
Although there are some technologies developed to improve the above-mentioned problems, the practice still encounters some difficulty, such as complicated machining procedures or too many kinds of components. So, it is still insoluble to reduce the influence of the defect of the outer circulation passage on the motion of the balls.
Therefore, it is an important subject to provide a linear motion module that has no sectional difference so as to increase the motion stability, reduce the noise and suit the high-speed motion.